Ken, Geoff is correct in what he says and your own compost can be used for potting on, enhancing the soil when planting new plants or as a mulch, it does contain goodness and will not come amiss.
Being taught to garden when bespoke seed mediums did not exist we did use our own composts and soil to set seed. Plus of course leaf mould. We used various means of sterilising the soil and they did work, from using a home made steamer, Jeye's fluid, a bucket on the bonfire ashes with soil in it or today an old micro wave in the garage, put some soil in a plastic container and blast it, works for me.
Seeds do not need nutrient so mixing a third soil, a third washed sand, a third grit will give a good seed compost, sow your seed wet it then put some fine grit on top and that is it.
As soon as the seeds have two true leaves i prick out into half compost half sand and grit mixed then as you pot on compost with some grit mixed in.
Think about it, we all sow seed straight onto a seed bed in the garden which is not sterelised and most come in fact we have to thin them out, self seeders pop up all over the place nature can look after her own, probably we fuss too much.
Frank.
